JPH04288453A - Freezing cycle device - Google Patents

Abstract

PURPOSE:To improve an operating efficiency by a method wherein means for detecting a lower pressure side pressure of a freezing cycle is provided, an output frequency of an inverter circuit is controlled in such a way as its detected value becomes a set value, an operating state of each of evaporators is detected and then the set value is changed. CONSTITUTION:Discharged refrigerant from a compressor 1 is supplied to evaporators 13, 23 and 33 through a condensor 2, a liquid tank 3, two-way valves 11, 21 and 31 and expansion valves 12, 22 and 32. A refrigerator chamber, an ice temperature chamber and a freezing chamber are cooled and then temperature sensors 14, 24 and 34 for use in detecting an inner temperature of each of the chambers are provided for detecting a load of each of the evaporators 13 to 33. Opening or closing of each of the two-way valves 11 to 31 is controlled by a controlling part in response to a load of each of the evaporators 13 to 33. A pressure sensor 8 for use in detecting a pressure of a low pressure side of a freezing cycle is provided and it is controlled such that an operating frequency of the compressor 1 is increased by a predetermined value when the detected pressure is increased more than its set value and then the aforesaid set value is selected in reference to the evaporator showing the lowest evaporating power.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle device used for showcases and the like.

0002

2. Description of the Related Art In stores that sell fresh foods, the foods are displayed in showcases to maintain the freshness of the foods.

[0003] This showcase has storage chambers for refrigeration,
There are several types that are used separately, such as those for ice temperature and those for freezing. In this case, the refrigeration cycle is equipped with an evaporator for cooling the high temperature zone, an evaporator for cooling the medium temperature zone, and an evaporator for cooling the low temperature zone. The evaporator for cooling the temperature range is installed in the ice room, and the evaporator for cooling the low temperature range is installed in the freezing room.

[0004] That is, a compressor, a condenser, a pressure reducer, and three evaporators that are parallel to each other and have different cooling temperature ranges are successively connected to form a refrigeration cycle. Then, the flow of refrigerant to each evaporator is controlled according to the load of each evaporator, and the low pressure side pressure of the refrigeration cycle (suction pressure of compressor 1) is detected, and the detected pressure is the set value. The operating frequency of the compressor (output frequency of the inverter circuit) is controlled so that

[0005] In this case, the set value is adjusted to the evaporation pressure of the evaporator with the lowest cooling temperature range, thereby ensuring sufficient cooling capacity for the freezer compartment with the heaviest load.

[0006]

[Problems to be Solved by the Invention] However, in the above-mentioned refrigeration cycle, as the load changes, the operation of the evaporator for low-temperature zone cooling stops, and the operation of the evaporator for high-temperature zone cooling or medium-temperature zone cooling stops. The evaporator may continue to operate.

[0007] In this case, the evaporation pressure becomes high, and therefore the low pressure side pressure is at a position considerably higher than the set value, and the operating frequency of the compressor is set high in an attempt to reduce it. This is a very inefficient operation and greatly impairs the energy saving effect.

[0008] This invention has been made in consideration of the above circumstances.
The purpose is to provide a refrigeration cycle device that can improve operating efficiency and, by extension, improve energy saving effects.

[0009]

[Means for Solving the Problems] A refrigeration cycle device of the present invention includes a refrigeration cycle in which a compressor, a condenser, a pressure reducer, and a plurality of evaporators having different cooling temperature zones are connected in parallel to each other.
a plurality of two-way valves provided in the refrigerant flow path to each of the evaporators;
means for opening and closing these two-way valves according to the load of each of the evaporators; an inverter circuit for outputting a voltage for driving the compressor; a means for detecting the pressure on the low pressure side of the refrigeration cycle; The apparatus includes means for controlling the output frequency of the inverter circuit so that the pressure is at a set value, means for detecting the operating state of each of the evaporators, and means for varying the set value in accordance with the detection result.

0010

[Operation] In the refrigeration cycle device of the present invention, the output frequency of the inverter circuit is controlled so that the pressure on the low pressure side of the refrigeration cycle becomes a set value, and the set value is changed in accordance with the operating state of each evaporator.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a variable capacity compressor, and the inlet side of a condenser 2 is connected to the discharge port of the compressor 1. On the outflow side of this condenser 2, a liquid tank 3, a two-way valve 11,
21, 31 and the inlet sides of the evaporators 13, 23, 33 are connected via pressure reducers such as expansion valves 12, 22, 32.

The outlet sides of the evaporators 13, 23, 33 are connected to the suction port of the compressor 1.

Here, the evaporators 13, 23, and 33 have different cooling temperature ranges; the evaporator 13 is used for cooling the high temperature range where the evaporation pressure (or evaporation temperature) is high, and the evaporator 23 is used for cooling the high temperature range where the evaporation pressure (or evaporation temperature) is high. The evaporator 33 is used for cooling in a medium temperature range where the evaporation pressure (or evaporation temperature) is moderate, and the evaporator 33 is used for cooling in a low temperature range where the evaporation pressure (or evaporation temperature) is low. As a specific example, the evaporation temperature of the evaporator 13 is (-10 degrees to -5 degrees), the evaporation temperature of the evaporator 23 is (-20 degrees to -10 degrees),
The evaporation temperature of the evaporator 33 is set at (-40 degrees to -30 degrees).

[0015] The storage room of the showcase is a refrigerator room (+5 degrees to +10 degrees) for storing fruits and vegetables and daily supplies, an ice room (-5 degrees to 0 degrees) for storing meat and fresh fish, and frozen foods. A freezer compartment (-30 degrees ~
-20 degrees), and the refrigerator room is equipped with an evaporator 13 for cooling the high temperature range, the ice room has an evaporator 23 for cooling the medium temperature range, and the freezing room has an evaporator 33 for cooling the low temperature range. .

The expansion valves 12, 22, 32 are connected to the temperature sensing cylinder 1.
2a, 22a, and 32a, and the degree of opening changes so that the difference between the temperature sensed by the temperature-sensing tube and the temperature of the refrigerant flowing through it becomes a constant value.

[0017] The temperature-sensitive cylinder 12 of this expansion valve 12, 22, 32
a, 22a, and 32a are attached to the outflow side pipes of the evaporators 13, 23, and 33, respectively. In other words, the expansion valves 12, 22,
32, the degree of superheating of the refrigerant in the evaporators 13, 23, and 33 is maintained at a constant value.

One end of a defrosting bypass 4 is connected to the discharge port of the compressor 1, and the other end of the bypass 4 is connected to the evaporator 13, 2.
3 and 33, respectively, are connected to the inflow sides. A two-way valve 5 is provided midway through the bypass 4.

A condenser fan 6 is provided near the condenser 2. In the vicinity of the evaporators 13, 23, 33, internal temperature sensors 14, 24, 34 and evaporator fans 15, 25,
35 respectively.

Furthermore, a pressure sensor 8 is attached to the low pressure side piping of the refrigeration cycle.

The control circuit is shown in FIG.

Reference numeral 40 denotes a commercial AC power source, to which a control section 41 and an inverter circuit 42 are connected.

The control section 41 is composed of a microcomputer and its peripheral circuits, and performs overall control of the refrigeration cycle apparatus.

This control section 41 includes two-way valves 5, 11, 21.
, 31, pressure sensor 8, evaporator fan motor 15M,
25M, 35M, internal temperature sensors 14, 24, 34, condenser fan motor 6M, and inverter circuit 42 are connected.

The inverter circuit 42 rectifies the voltage of the power source 40, converts the rectified voltage into a voltage of a predetermined frequency according to a command from the control section 41, and outputs the voltage. This output is supplied to the compressor motor 1M as a driving voltage.

The control section 41 includes the following functional means.

(1) Means for controlling the opening and closing of the two-way valve 11 by comparing the temperature detected by the internal temperature sensor 14, which is the cooling load of the refrigerator compartment, with a set value ±α (α is a difference).

(2) Means for controlling the opening and closing of the two-way valve 21 by comparing the temperature detected by the internal temperature sensor 24, which is the cooling load of the ice room, with a set value ±α.

(3) Means for controlling the opening and closing of the two-way valve 31 by comparing the temperature detected by the internal temperature sensor 34, which is the cooling load of the freezer compartment, with a set value ±α.

(4) Means for controlling the operating frequency F of the compressor 1 (output frequency of the inverter circuit 42) so that the pressure Ps detected by the pressure sensor 8 becomes the set value P1.

(5) Means for detecting the operating state of the evaporators 13, 23, 33 based on the opening/closing control of the two-way valves 11, 21, 31.

(6) Means for varying the set value P1 based on the detected operating state and set value selection conditions previously stored in an internal memory.

(7) Means for periodically opening the two-way valve 5 for a certain period of time to carry out so-called hot gas defrosting of the evaporators 13, 23, 33.

Next, the operation of the above configuration will be explained.

When the compressor 1 starts up, its discharged refrigerant enters the condenser 2. In the condenser 2, the refrigerant emits heat to the outside air and condenses.

The refrigerant that has passed through the condenser 2 is transferred to a liquid tank 3,
It passes through two-way valves 11, 21, 31 and expansion valves 12, 22, 32 and enters evaporators 13, 23, 33. In the evaporator 13,
The refrigerant absorbs heat from the air inside the refrigerator and evaporates. In the evaporator 23, the refrigerant takes heat from the air in the ice room and evaporates. In the evaporator 33, the refrigerant takes heat from the air in the freezer compartment and evaporates.

[0037] In this way, the refrigerator compartment, ice room, and freezing compartment are cooled.

The refrigerant that has passed through the evaporators 13, 23, and 33 is sucked into the compressor 1.

During operation, the internal temperature of the refrigerator compartment in which the evaporator 13 is installed is detected by the internal temperature sensor 14.

The control unit 41 closes the two-way valve 11 to block the refrigerant from flowing into the evaporator 13 when the temperature detected by the internal temperature sensor 14 falls below the "set value -α". after that,
When the detected temperature becomes higher than “set value + α”, two-way valve 1
1 to restart the flow of refrigerant into the evaporator 13.

The flow rate of the refrigerant is adjusted by the expansion valve 12 so that the degree of superheat of the refrigerant flowing through the evaporator 13 remains constant.

The internal temperature of the refrigerator compartment in which the evaporator 23 is installed is detected by the internal temperature sensor 24 .

The control unit 41 closes the two-way valve 21 to block the refrigerant from flowing into the evaporator 23 when the temperature detected by the internal temperature sensor 24 falls below the "set value -α". after that,
When the detected temperature becomes higher than “set value + α”, the two-way valve 21
is opened to restart the flow of refrigerant into the evaporator 23.

Note that the flow rate of the refrigerant is adjusted by the expansion valve 22 so that the degree of superheat of the refrigerant flowing through the evaporator 23 remains constant.

The internal temperature of the refrigerator compartment in which the evaporator 33 is installed is detected by the internal temperature sensor 34 .

When the temperature detected by the internal temperature sensor 34 falls below the "set value -α", the control unit 41 closes the two-way valve 31 and blocks the refrigerant from flowing into the evaporator 33. after that,
When the detected temperature becomes higher than “set value + α”, the two-way valve 31
is opened to restart the flow of refrigerant into the evaporator 33.

Note that the flow rate of the refrigerant is adjusted by the expansion valve 32 so that the degree of superheat of the refrigerant flowing through the evaporator 33 remains constant.

On the other hand, the control section 41 checks the operating states of the evaporators 13, 23, 33 based on the opening/closing control of the two-way valves 11, 21, 31, as shown in the flowchart of FIG. Then, the operating states of the evaporators 13, 23, and 33 and the setting value selection conditions (○
The set value P is based on
1 is made variable.

That is, the set value P1 is 3.3 kg/cm2 G, which corresponds to the evaporation pressure of the evaporator 13 (evaporation temperature "-10 degrees to -5 degrees"), and the evaporation pressure of the evaporator 23 (evaporation temperature "-10 degrees"). -20 degrees to -10 degrees”) 2.0
Kg/cm2 G, evaporation pressure of evaporator 33 (evaporation temperature "
-40 degrees to -30 degrees”) 0Kg/cm2 G
We have three options available. For example, the evaporator 13,
When all 23 and 33 are operating, set value P1
Select 0Kg/cm2 G as. When only the evaporator 23 is operating, the set value P1 is 2.0 kg.
/cm2 Select G. When only the evaporator 33 is operating, 3.3 kg/cm2 G is selected as the set value P1.

Furthermore, the pressure sensor 8 detects the low pressure side pressure (
The suction pressure (Ps) of the compressor 1 is detected, and when the detected pressure Ps becomes higher than the set value P1, the operating frequency F of the compressor 1 is increased by a predetermined value ΔF. When the detected pressure Ps becomes lower than the set value P1, the operating frequency F of the compressor 1 decreases.
is lowered by a predetermined value ΔF. Detected pressure Ps is set value P1
If it is equal to F, the operating frequency F of the compressor 1 is maintained as it is.

In this way, as shown in FIG. 5, the low pressure side pressure Ps converges toward the set value P1.

In this way, the set value P is set based on the evaporator with the lowest evaporation pressure among the evaporators in the operating state.
By selecting P1, the difference between the evaporation pressure and the set value P1 becomes small, and therefore each chamber can be cooled to an optimal state without setting the operating frequency F of the compressor high.

[0053] That is, efficient operation is possible;
It is possible to improve the energy saving effect.

Although each of the above embodiments has been explained using a showcase as an example, the present invention can be similarly applied to a refrigerator-freezer or an air conditioner. Moreover, although the case where the number of evaporators is three has been described as an example, there is no limitation to the number.

[0055]

[Effects of the Invention] As described above, according to the present invention, there is provided a refrigeration cycle in which a compressor, a condenser, a pressure reducer, and a plurality of evaporators with different cooling temperature zones are connected in parallel, and a a plurality of two-way valves provided in the refrigerant flow path; means for opening and closing these two-way valves according to the load of each of the evaporators; an inverter circuit that outputs a voltage for driving the compressor; means for detecting the low pressure side pressure of the refrigeration cycle;
A means for controlling the output frequency of the inverter circuit so that the detected pressure becomes a set value, a means for detecting the operating state of each of the evaporators, and a means for varying the set value according to the detection result. Therefore, it is possible to provide a refrigeration cycle device that can improve operational efficiency and, by extension, improve energy saving effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a refrigeration cycle according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a control circuit of the same embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a diagram showing a format of setting value selection conditions in the same embodiment.

FIG. 5 is a diagram showing an example of changes in operating frequency F and low pressure side pressure Ps in the same embodiment.

[Explanation of symbols]

1... variable capacity compressor, 2... condenser, 11, 21, 31...
Two-way valve, 13, 23, 33... Evaporator, 41... Control unit, 4
2...Inverter circuit.

Claims (1)

[Claims] [Claim 1] A refrigeration cycle in which a compressor, a condenser, a pressure reducer, and a plurality of evaporators with different cooling temperature zones are connected in parallel to each other, and a plurality of two-way channels provided in a refrigerant flow path to each of the evaporators. a valve, means for opening and closing these two-way valves according to the load of each of the evaporators, an inverter circuit for outputting a voltage for driving the compressor, and a means for detecting the pressure on the low pressure side of the refrigeration cycle. , means for controlling the output frequency of the inverter circuit so that the detected pressure becomes a set value, means for detecting the operating state of each of the evaporators, and means for varying the set value according to the detection result. A refrigeration cycle device characterized by: